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Equilibrium appeared 35 times across 3 years — 4.1% of Chemistry. This question is from Chemical Equilibrium and Kp calculation.

Year 2026 2025 2024 Total
Questions 10 17 8 35

37.8 ~g ~N₂ O₅ was taken in a 1 ~L reaction vessel and allowed to undergo the following reaction at 500 ~K: 2 N _ 2 O _ 5 (g) leftharpoons 2 N _ 2 O _ 4 (g) + O _ 2 (g) The total pressure at equilibrium was found to be 18.65 bar. Then, Kp = _ _ _ _ × 10⁻² [nearest integer] Assume N₂O₅ to behave ideally under these conditions Given: R = 0.082 bar L mol⁻¹ K⁻¹

Numerical Answer Type:
Enter a numerical value Answer: 962 to 962 +4 marks

Solution & Explanation

Related Formula
P = (nRT)/(V) and Kₚ = (PN₂O₄)² · PO₂(PN₂O₅)²
Core Logic

First, find the initial moles of N₂O₅ using its molar mass (108 g/mol):

n₀ = (37.8)/(108) = 0.35 moles

Using the ideal gas equation, compute the initial pressure (Pᵢ):

Pᵢ = (0.35 × 0.082 × 500)/(1) = 14.35 bar

Setting up the equilibrium partial pressures table: arraylccccc & 2N₂O5(g) & leftharpoons & 2N₂O4(g) & + & O2(g) Initially: & 14.35 & & 0 & & 0 At equilibrium: & 14.35 - 2P & & 2P & & P array

The total pressure at equilibrium is given as:

Ptotal = (14.35 - 2P) + 2P + P = 14.35 + P = 18.65 bar P = 18.65 - 14.35 = 4.3 bar

Now, calculate the equilibrium partial pressures for each component:

  • PN₂O₅ = 14.35 - 2(4.3) = 5.75 bar
  • PN₂O₄ = 2(4.3) = 8.6 bar
  • PO₂ = 4.3 bar
  • Substitute these partial pressures into the Kₚ expression:

Kₚ = ((8.6)² × 4.3)/((5.75)²) = (73.96 × 4.3)/(33.0625) ≈ 9.619

Expressing the result in the requested format (x × 10⁻²):

Kₚ = 961.9 × 10⁻²

Rounding to the nearest integer yields 962.

Pattern Recognition

Always calculate the initial pressure first using the ideal gas law (PV=nRT). This provides a clear baseline for tracking equilibrium partial pressures.

Chapter Mix

Class 11 Chemistry: Equilibrium

More Equilibrium Previous-Year Questions — Page 7

Q84 jee_main_2024_29_jan_morning Kp and Kc Relationship
For the reaction N₂O₄(g) leftharpoons 2NO₂(g) Kₚ = 0.492 atm at 300K . Kc for the reaction at same temperature is ______ × 10⁻² . (Given: R = 0.082 L atm mol⁻¹ K⁻¹)
Numerical Answer. Answer: 2 to 2

Solution

Related Formula
Kₚ = Kc · (RT)Δ ng
Core Logic

For the given gaseous equilibrium reaction:

N₂O₄(g) leftharpoons 2NO₂(g)

First, find the change in the number of moles of gas (Δ ng):

Δ ng = nₚ - nᵣ = 2 - 1 = 1
Step 1: Calculation

Substitute the given values into the Kₚ - Kc relationship: Kₚ = 0.492 R = 0.082 T = 300 K

0.492 = Kc · (0.082 × 300)¹ Kc = (0.492)/(0.082 × 300) Kc = (0.492)/(24.6)

Kc = 0.02

Converting to the requested format (x × 10⁻²):

Kc = 2 × 10⁻²

So, the value is 2.

Chapter Mix

Class 11 Chemistry: Equilibrium

Q85 jee_main_2024_30_january_evening Buffer Solutions
The pH of an aqueous solution containing 1M benzoic acid (pKₐ = 4.20) and 1M sodium benzoate is 4.5. The volume of benzoic acid solution in 300 mL of this buffer solution is ______ mL.
Numerical Answer. Answer: 100 to 100

Solution

Related Formula

Henderson-Hasselbalch Equation for Acidic Buffers:

pH = pKₐ + ( [Salt][Acid] )
Core Logic

Let the volume of 1M Benzoic acid be Vₐ mL and the volume of 1M Sodium benzoate be Vₛ mL. Total volume = Vₛ + Vₐ = 300 mL.

Millimoles of acid = 1 × Vₐ = Vₐ Millimoles of salt = 1 × Vₛ = Vₛ

Applying Henderson's Equation:

4.5 = 4.2 + ((Vₛ)/(Vₐ))
Step 1: Calculate Volume Ratio
((Vₛ)/(Vₐ)) = 4.5 - 4.2 = 0.3

Since 2 ≈ 0.3, we have:

(Vₛ)/(Vₐ) = 2

Vₛ = 2 Vₐ

Step 2: Substitute and Solve

We know Vₛ + Vₐ = 300 Substituting Vₛ = 2 Vₐ:

2 Vₐ + Vₐ = 300

3 Vₐ = 300

Vₐ = 100 mL
Chapter Mix

Class 11 Chemistry: Equilibrium

Q82 jee_main_2024_30_jan_morning Solubility Product
The pH at which Mg(OH)₂ [Kₛₚ=1× 10⁻¹¹] begins to precipitate from a solution containing 0.10 M Mg²⁺ ions is
Numerical Answer. Answer: 9 to 9

Solution

Related Formula
Kₛₚ = [Mg²⁺][OH^-]² pOH = - [OH^-]

pH + pOH = 14

Core Logic

Precipitation begins just when the ionic product equals the solubility product (Qₛₚ = Kₛₚ).

Step 1: Calculating required [OH-]
[Mg²⁺][OH^-]² = 10⁻¹¹

Given [Mg²⁺] = 0.10 M

0.10 × [OH^-]² = 10⁻¹¹ [OH^-]² = 10⁻¹⁰ [OH^-] = 10⁻⁵ M
Step 2: Finding pH
pOH = - (10⁻⁵) = 5

pH = 14 - pOH pH = 14 - 5 = 9

Chapter Mix

Class 11 Chemistry: Equilibrium

Q71 jee_main_2024_31_jan_evening Equilibrium Constants (Kp and Kc)
A(g) leftharpoons B(g) + (C)/(2)(g) The correct relationship between KP, α and equilibrium pressure P is
  • A. KP = α(1)/(2)P(1)/(2)(2 + α)(1)/(2)
  • B. KP = α(3)/(2)P(1)/(2)(2 + α)(1)/(2)(1 - α)
  • C. KP = α(1)/(2)P(3)/(2)(2 + α)(3)/(2)
  • D. KP = α(1)/(2)P(1)/(2)(2 + α)(3)/(2)

Solution

Related Formula
KP = PB · (PC)(1)/(2)PA

where Pᵢ is the partial pressure of component i.

Step 1: Setting up the ICE Table

For the reaction A(g) leftharpoons B(g) + (1)/(2) C(g)

Let initial moles of A = 1. At equilibrium: Moles of A = 1 - α Moles of B = α Moles of C = (α)/(2)

Total moles at equilibrium = (1 - α) + α + (α)/(2) = 1 + (α)/(2) = (2 + α)/(2)

Step 2: Calculating Partial Pressures

Using mole fraction × Total Pressure (P): PA = (1 - α)/(1 + (α)/(2)) · P PB = (α)/(1 + (α)/(2)) · P PC = ((α)/(2))/(1 + (α)/(2)) · P

Step 3: Calculating Kp
KP = PB · (PC)(1)/(2)PA KP = ( (α)/(1 + α/2) P ) · ( (α/2)/(1 + α/2) P )1/2(1 - α)/(1 + α/2) P KP = α · (α/2)1/2 · P3/2(1 + α/2)3/2 · (1 + α/2)/((1 - α) P) KP = α3/2 · P1/2√(2) · (1 + α/2)1/2 · (1 - α)

Since 1 + α/2 = (2+α)/(2), the √(2) in denominator cancels out perfectly leaving:

KP = α(3)/(2) P(1)/(2)(2 + α)(1)/(2)(1 - α)
Chapter Mix

Class 11 Chemistry: Equilibrium

Q62 jee_main_2024_31_jan_morning Equilibrium Constant
For the given reaction, choose the correct expression of KC from the following :- Fe(aq)³⁺ + SCN(aq)⁻ leftharpoons (FeSCN)(aq)²⁺
  • A. KC = [FeSCN²⁺][Fe³⁺][SCN⁻]
  • B. KC = [Fe³⁺][SCN⁻][FeSCN²⁺]
  • C. KC = [FeSCN²⁺][Fe³⁺]²[SCN⁻]²
  • D. KC = [FeSCN²⁺]²[Fe³⁺][SCN⁻]

Solution

Related Formula
KC = [Products][Reactants]
Core Logic
KC = Products ion conc.Reactants ion conc. KC = [FeSCN²⁺][Fe³⁺][SCN⁻]
Chapter Mix

Class 11 Chemistry: Equilibrium

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